- Diode Test Range In Digital MultimeterPosted 374 days ago
Electronics Repair Questions/Answers and Testimonials -Part 68
finally i repaired the set, it was a difficult situation as i was in a tight corner but i did not want to give up, i followed your suggestion on verifying the the supply voltage on the vertical ic was ok, on tracing the voltage from the one LOPT secondary side i came across one flame proof 30ohm resistor in series whit the line, when i did voltage testing on the line a diode before the resistor has 46.7volts, when tested after the resistor i got 14.3volts, when i pulled one leg of the resistor(the side that gave me 14.3volts) and tested there was no voltage, i removed the resistor and tested behold it was open, i replaced and powered and instantly the new resistor flamed, i removed it, and one by one i pulled one leg of all the components on that line(6 diodes and 7 capacitors) and tested one by one, be hold ,i find one diode that looks like zener diode whit code 4531 shorted, i replaced whit 1N4841 soldered back all the other removed legs and powered, the set and it comes on as clean as new. in fact i was very happy, i just want to tell you the good news and to thank you for your numerous supports and suggestions, thanks and GOD bless.
Thank u very much. I haven’t notify yet the owner of the LCD unit because im waiting for your reply. I’m happy that beyond some doubts i can slowly analyze LCD TV repair.
Actually, I do accept repairing LCD monitor only. Im still afraid to accept big LCD TV repair because I am not familiar with it yet. but soon or maybe I have to encourage now myself accepting big LCD TV because of your helpful site.
I also told some of my friend here long before regarding your website & i think they began contacting you.I would just continually disseminate ur company because of your unselfish skills you are sharing w/ other technicians.
I say thank you again & God bless you and your family.
Thank you for your encouragement. I was able to fix three smps and I already used it in three computer that I’ve ressurrected, then I give it to one of my pastor friend who had no personal computer. The other two was working again and two of our young people was so thankful they were able to used their own computer again with just small amount of money spent to buy some e-cap. Thank you again. God bless..
Thank you very much Jestine for the November Newsletter particularly for the article from Humphrey which is very concise, clear and educative. It will help many electronics repair guys a lot. I leave not very far from Humphrey’s place. Iam in Malawi in Central Africa.
Your articles Jestine are really professional and continue to glorify God by giving the masses some useful tips in electronics repair work.
Good day and God bless you abundantly.
Good day Justine,I recieved your email its very helpfull to me.because its worth it.I felt that, i am a Proffesional technician.I replaced the vertical output ic.no more half picture.easy money to be earned for that jestine, your a good mentor,your great.God bless you.
Your DVD player article by Mr. Kimathi is good and interesting.
Appreciate the way you connect and brings us such interesting articles.
DVD players are found in most households. So, it was helpful.
I have not found a “Practical Electronics Teacher” like you. Now, in my office my all friends call me “Practical Engineer” and that’s because of you only.
i measure an 470 uf/10v electrolytic capacitor with digital
capacitance meter and esr meter. the capacitanc meter showed 460uf and
esr meter 5.1 ohm.
is the capacitor defective or not?
Yes it is defective. If you are unsure you can always compare with a good one.
i have tested some electrolytic capacitors with capacitance meter and
measured value is higher than normal value. for example i tesed an
470uf electrolytic capacitor and capacitance meter showed 520 uf . has
the capacitor problem?
I came across such cap too but the cap is still functioning. If it get lower then you need to change it and if the value is higher and the set is working then you can ignore it.
how much deacreased capacitance value(what percent) is allowable for
electrolytic capacitor and non polarity(ceramic and etc) capacitors ?
To make it easy to remember- i take minus 10% as a guideline.
Thanks very much for your monthly report newsletter.For past month i
have managed to repair three LCD monitors
One was brige rectifier,had a short on ac in and positive out.
Second was 16 v 1000uf capacitors.
lastly it was the VGA input PCB, all were Fratronic LG monitors
through your help i have build confidence on my work
Hello Mr Jestine Yong.
Thanks for sending me your monthly repair updates…
Sir can i ask for your opinions about a tv set that been slightly hit by lightning..
Can this tv set posibly work again sir?
Where will be the most damage part sir?
Thanks again and i hope you can have time to reply my letter sir…
When a tv hit by lightning you need to check the power section especially the fuse and the semiconductor like bridge rectifier and power fet/ic. Sometimes a too severe burn could cause the tv to be beyond repair.
I would like to thank you for the articles you’ve sent, it’s very helpful. I was wondering if you could give some advise on how start with a service center business. I am planning to have one here in our place. It’s some kind of Electronics and Computer servicing maybe,just give some sort of advise please.
I suggest that you run the business from your house first. Once you have established your customer base and have good cash flow then only you rent a shoplot which is much more presentable.
I bought the book “testing electronic components” and I can’t find a better book its wonderful!
Hope you are doing well. I’m on the way repairing a Sony TV model KV-PF21L70. Already 2 days I’m trying to check for the problem. My other problem also is that no available schematic diagrams. The TV problem was too much green on the display. The first component i found with problems was the 6.1k resistor per color along CRT board, (change value problem). After changing this bad components, only a little bit improvements, But still green color is very strong. I did not also find any leak caps. After re soldering all components but still problem exist. I had only one suspect remaining and I need your opinion regarding this one, CXP86499 IC. Possible this one was the problem?
It can be that ic but there are two more things that you need to consider- a weak tube and a corrupted eeprom data.
Thanks for this months newsletter, this is what i am looking for. i always encounter no disc problem. this
is very common problem in both VCD, DVD some time even CD, I always think is the lence problem. after changing
not long it come back again. i am looking very hard for this solution. finally i got it from you. very thanks for this issue.
Next I am looking for the projector repair solution. any loban for this.
Very Best regards
hi Jestine complement of the season, just to let you know you are
doing a wonderful job, on the subject on DVD i find it to be very
informative keep up the good work.
there are many ttl or cmos ics in some circuit boards. how can i know
that which one is defective?
You need to use logic probe and a logic pulser to test it with the help of truth table.
what is the best practical way to test opamps(operational amplifier)?
Oscilloscope or voltage testing.
If it is a color patches problem then you can use a demagnetizer to remove it. If it can’t be removed then the picture have problem. Make sure also the posistor is working and no dry joints.
Thanks very much for that support on dvd, this are always the problems of dvd no disc, we are proud of you Jestine God bless you more, i was repairing on samsung 29 inches tv, the model is CS-29Z40MH, it was power problem but now the tv is coming on, on the screen there is ring like a ball with different colors, i want advice from you what might be the cause.
thak you sir!
i wonder if you can also give me some idea about zener diode markings and value…
Try here http://www.jestineyong.com/?p=2549
remember to read the comment.
Good day Jestine,the b+ is not normal. I found out that the power regulator ic is burn out.The value is STR-W6554A. and a zener diode IN4148.another successfull job jestine.because of you i learn a lot.Im very thankfull.God bless.
Thank you for the immediate concerning my problem. I did replace almost all primary components which includes even the transformer as well as the start up resistor (.18ohms) and I am sure pretty sure the replaced components were new and some are all tested working from other SMPS. I also used EDS cap analyzer for searching leaking and bad capacitor on the secondary line as well as the output portion of the SMPS. I replaced all the error amplifier as these might also cause the problem but still it didn’t solved. Not to mentioned I also replaced the -12 volts voltage regulator as well as the inductor coil and all three opto-isolators bridging primary line to secondary line. I did trace the line going to the feedback of the PWM controller and replaced all components on it. Also, I have replaced the ultra fast diode at the secondary line of the SMPT which you might not able to see on my picture because it is covered by the heat sink.
I am running out of idea jestive and hoping you can help me on this problem. I have 4 SMPS with the same issue and with the same brand as well.
Noted. I have seen this kind of problem before but not in your model that everything check to be good in the primary and secondary output side. After the replacement of the secondary side IC TL494 the power supply came back to life. Since you said you have checked all components in the power side then you may need to check the components in the secondary side as well.
One more thing, certain power supply need to connect to the original motherboard in order to turn it on. I came across few brands in the market where the power supply fan will turn for a while and shutdown. That time i was using a dummy motherboard with hardisk and etc. Putting back the power supply to the original casing solved the problem.
Hi! Hope you are in good health. Thank you very much for the November newsletter you send to me. This tip is very helpful for me because there are lot’s of DVD player that come in for repair on my shop. I need this info very badly. Thank you very much Jestine. You are the man… More power and God Bless!
Dear Jestine Yong,
Your ebook ” Discover The Secrets How I Repair BenQ And The Acer 17″ LCD
Problems”, it is very helpfull for learning to repair LCD. I have a BenQ
DV3250 which problem with 2 seconds backlight off,
I just not sure where is the section of the feedback circuit area, would you
kindly show me so I can use your method try solve the
problem? By the way, this is my first project with LCD.
The feedback section can be traced from the backlight connector. One line coming from the high voltage transformer and the other line is going back to a circuit and that circuit is the feedback circuit. Display shutdown can be due to bad backlight, dry joints in high voltage transformer or bad e-caps.
hope u fine.
I got a Dell monitor in dead condition.While checking around the horizontal section(B+).,i found Q312,R371,Q311,Q310 had gone bad.I replaced those parts and powered up the monitor.
Now the problem is.,after switching ‘ON’ the monitor, Display comes out wit pincusion effect for a couple of seconds and the FET(Q312)(replaced with IRF630) gets shorted followed by a “crick..crick” sound.
what will be the cause..do guide me please.
Check the B+ coil (L301) with ring tester and if possible check all components that is corresponding to the fet like D318, C323 and also makes sure the flyback primary winding is good and not shorted.
Finally, I have found the culprit on the SMPS. It is the start up resistor (.18ohms/1w). I noticed the fluctuation of readings on its resistance as well as its voltage drop. I didn’t noticed this earlier because I tested the resistor okay before switching it on. And when I re-test it again using my multimeter after the testing procedure the resistor tend to change it resistance value. My only problem now is the replacement of these value. I have 5 SMPS with same problem and I have searched all over the market here in our country (OMAN) and I haven’t found any. I tried replacing the resistor with 0.39ohms/1w which is the available one but it didnt work at all. Please help me find the closest equivalent replacement value of these resistor. Thank you very much. God Bless
You can infact test the low ohm resistor with Blue esr meter. That was the current sense resistor and not start up resistor. From the previous email i did mentioned to check on this resistor because it is very sensitive. Since you can only find a 0.39 ohm resistor then you can parallel it to become 0.18 ohm value. If you could find a lower value resistor than 0.18 ohm then you can use it too.
Have a good day!
Actually I got these voltages at CRT board:
G1 -67 V
G 67 V
G2 254 V
Heater 6.04 V
others at that moment cannot be measured because being covered by shielding plate.
Because I got 254 V at G2, so I didn’t adjust the g2 knob.
Yes you need to tur the knob as sometime the tube can get weak and it need higher g2 voltage in order to have display.
Recalling your article about ” The Secrets on How to Testing FBT or LOPT, which says that internal capacitor should have capacitance value between 1.5 nF or above, do you think this monitor ( only 0.5 nF internal capacitance value ) will work normally and will last long? Since I don’t think I could get the FBT replacement, is this monitor worth further repairing efforts?
Usually it won’t last long and it will cause tik -tik sound too and the display will comes and go. I suggest that you don’t further to repair this monitor. However, if you want to learn how to solve the display problem you can go ahead to test out your skill.
How are you?
I’m fine thank you.
I was thinking about buying a blue ring transformer tester from you but I don’t know if it’s usable for testing inverter HV transformers.
Yes it is suitable to test on inverter HV transformer because i have used it to test on the LCD Monitor transformer.
Do you know of any other testing method or circuitry used for testing these transformers. There is something called oscilloscope ring test. I’m sure you’ve heard about it? If you would be as kind as to build a circuit like this for me, I would pay you ok for it.
Try this link:
the voltages on vertical ic LA78041 are as follows: pin # 1-2.5v, #2-27v. #3-1.2v,(#4-ground) #5-14.6v,#6-26.5v,#7-2.5v
There is supply voltage but you may need to replace one and retest.
voltages on EEPROM pin nos.(1,2,3,4,7-ground), pin #5 and 6-4.5v, #8-5.1v.
Voltage is good but it does not guarantee the data is good or corrupted. You need to replace with the same IC that have programs in to compare.
i`ve check other site and in some branded tv EEPROM can be reset(thru service mode?)
Yes but you need to know how to enter the service mode.
is there any replacement ic for a specific EEPROM ic?
The best is to use back the same part number because getting eeprom ic is not hard.
one technician told me i can replace 24C08 with 24C16 and i tried it but nothing change.thank you and best regards.
Some equipment can be replace with a higher number but others don’t. The best is to replace with the same part number with the same data in it.
I am really glad and appreciate your effort on helping me. I finally solved the problem and fixed all 5 IBM SMPS. I take your advised and used 0.39ohms resistor paralleled to .18ohms resistor and it was perfectly working. Unfortunately, I am not aware that I can used a BLue ring ESR meter for testing such problem. Hope you can teach me as well.
You need Blue ESR meter to test the low ohm resistor and not the Blue Ring Tester. Just place the probes on the resistor pins and read the result. It is easy.
hi i am rik.i have lg15″ crt monitor.its verticle position blingking.
i replace verticle ic but steel blingking.pleace see vidio for
details.what its solution.
From the video i saw both side shaking. First you need to check if the output voltages from the power supply are good and stable or not. If not stable then check the big filter cap in the primary power side.
Cold you say if a 19″ inch tv has a horizontal linearity coil and what would be the symtomps of a bad coil?
Either the left or right side of the display is small than the other side.